1. Field of the Invention
The present invention relates to modified clay, and in particular relates to a flame-retardant clay-polymer composite formed by using the modified clay.
2. Description of the Related Art
Polymer materials are used in a wide variety of applications, such as electronic devices, construction materials, automobile materials, daily necessities products and so on. Take electronic package applications as an example, electronic packages are used to integrate and package a plurality of semiconductor integrated circuits. Electronic packages provide functions of electrical power transmission, signal transmission, heat dissipation, protection, and structural support. For electronic package applications, thermosetting resins, such as epoxy, are frequently used to serve as a printed circuit board material. Usually, a composite material substrate is used to form a printed circuit board. Strengthening fibers, such as glass fibers, are combined with the resin to form the composite material substrate. Composite materials are capable of providing excellent mechanical strength and size stability.
However, due to inherent material characteristics of polymer materials, after being heated, polymer materials may be easily damaged by softening or burning. In conventional techniques, to solve the problem mentioned above, a flame retardant including a high amount of bromine, such as brominated resin, is added into polymer materials. Although adding brominated resin is helpful for flame retardation, after being heated, polymer materials with brominated resin will produce a lot of smoke and even generate hydrogen halide or dioxin with corrosiveness and toxicity, causing serious environmental problems. Halogen and phosphate free methods are desired to produce flame retardant polymer materials.
U.S. Pat. No. 4,708,975 and U.S. Pat. No. 4,826,899 disclose a copolymer comprising an organophilic clay and a flame retardant containing halogen. The clay is added to the copolymer to increase the formation of a coke layer. U.S. Pat. No. 6,414,070 discloses adding an organic modified clay to a copolymer to improve a self extinguishing property during an MVSS-302 test.
Other patents using clay to improve flame-retardant properties of polymer materials comprise U.S. Pat. No. 6,011,087, U.S. Pat. No. 6,414,070, U.S. Pat. No. 5,779,775, U.S. Pat. No. 6,025,421, U.S. Pat. No. 6,180,695, U.S. Pat. No. 4,708,975, U.S. Pat. No. 4,826,899, U.S. Pat. No. 4,582,866, U.S. Pat. No. 6,610,770, U.S. Pat. No. 5,104,735, U.S. Pat. No. 4,107,376, U.S. Pat. No. 6,207,085, U.S. Pat. No. 4,273,879, U.S. Pat. No. 5,886,072, U.S. Pat. No. 4,981,521, U.S. Pat. No. 5,686,514, U.S. Pat. No. 5,473,007, U.S. Pat. No. 4,472,538, U.S. Pat. No. 3,953,565, U.S. Pat. No. 4,070,315, U.S. Pat. No. 5,863,974, U.S. Pat. No. 5,773,502, U.S. Pat. No. 5,204,395, U.S. Pat. No. 5,294,654, U.S. Pat. No. 5,153,251, U.S. Pat. No. 4,639,486, U.S. Pat. No. 4,386,027, U.S. Pat. No. 4,373,047 or U.S. Pat. No. 4,280,949 and so on. For the patents, flame-retardant properties are improved, by adding flame retardants with halogen, phosphate, or antimony oxide. Although the added clay may produce the coke layer, the improvement in flame-retardant properties is achieved mainly by adding other inorganic materials or flame retardants to the polymers.